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Improvement Ratio

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Roy Halladay has had a rocky start to his exhibition season, but in 2000, he experienced far greater struggles in games that counted. Just over a decade ago, Rany Jazayerli covered both that disastrous season and the impressive turnaround that followed it in the article reproduced below, which originally ran as a "Doctoring the Numbers" column on March 6, 2002.

Sure, a 5-3 record and a 3.16 ERA in 105 innings doesn't look that impressive on the surface...unless you consider that Halladay had a 10.64 ERA in 68 innings in 2000, the worst ERA in major-league history for someone with even 40 innings. Here is a list of the worst single-season ERAs since 1900:

Halladay improved his ERA by 7.48 points in 2001, which--not surprisingly--is a record for anyone with 50 or more innings in two consecutive seasons. What is surprising is the margin by which this is a record:

(On a pure percentage basis, it's hard to imagine anyone cutting their ERA by more than Ferdie Schupp, who sliced 82% off his ERA in 1916. He threw just 140 innings in 1916, preventing him from holding the single-season record for ERA.)

It's not just Halladay's massive improvement in his ERA that is so eye-catching, though. After all, looking at Halladay's career numbers, his 2000 season stands out for its overall suckitude. In 1999, Halladay had 3.92 ERA; he gave up just three earned runs in 14 innings in his 1998 cup of coffee, and came within an out of a no-hitter on the season's final day.

No, what makes Halladay's 2001 performance stand out in bold relief from the rest of his career is not his ERA. It's his strikeout-to-walk ratio.

Moreover, this fits perfectly with the trend Halladay showed in the minors, where he was considered a top prospect despite his maddeningly unimpressive strikeout-to-walk ratios in Triple-A. In 1998, he had 71 strikeouts against 53 walks; in 1997, he had 64 strikeouts against 53 walks. (In fairness, his ratios in the low minors were much better.)

Going into 2000, Halladay's career K/BB ratio in the majors was just 1.13. To put that in perspective, the lowest K/BB ratios of any active pitcher (min: 200 IP) through 2000 were:

Greg Maddux and Bret Saberhagen, these guys are not. These five pitchers include a pair of knuckleballers and a Rocky Mountain refugee, and what a man with Halladay's stuff was doing on this list isn't entirely clear. To his credit, last season he orchestrated one of the most impressive leaps in K/BB ratio in history.

That's a remarkable difference. Halladay more than tripled his career strikeout-to-walk ratio in 2001. That's more than remarkable: it's historic. The following chart lists the greatest improvements in K/BB ratio over a pitcher's previous career norms. To qualify, a pitcher had to throw at least 100 innings in his year of improvement, and have at least 200 previous career innings:

Halladay ranks eighth behind a group of veteran pitchers who suddenly stopped walking people entirely (Cy Young actually qualifies for the list again in 1905, but he was excluded for the sake of brevity.)

There's another way to construct this study. K/BB ratio is a wonderful metric, but it is subject to distortion at the extremes. In particular, a pitcher who is able to cut his walks down to a bare minimum can dramatically increase his K/BB ratio even if his strikeouts don't budge. Consider a pitcher with 20 walks and 70 strikeouts, a ratio of 3.50. If he adds 10 strikeouts to his total, his ratio inches up to 4.00. On the other hand, if he cuts 10 walks, his ratio doubles to 7.00. Hal Brown didn't suddenly turn the corner at age 38. In his "breakout season," he struck out 68 batters in 141 innings, less than one every other inning. But because his control was freakishly impeccable for one fluky season (just 0.57 walks per nine innings), he reached the top of the previous chart.

That's not what Halladay did. Halladay's performance--cutting his walk rate and increasing his strikeout rate--was far more impressive. So instead of comparing strikeouts to walks, let's compare each of them to innings pitched.

Halladay cut his previous career walk rate by more than two-and-a-half walks per nine innings, and increased his strikeout rate by an even higher margin. If we take the weighted average of the two (using an identical process to the one that turns homers and stolen bases into Bill James' Power-Speed number), we arrive at an "Improvement Ratio" of 2.72. This is the highest recorded by any pitcher, at any age, in major-league history.

Todd Van Poppel standing side-by-side with Randy Johnson, Charlie Puleo giving back cuts to Duane Ward...that's, um, a rather eclectic group of pitchers.

In general, the fluke seasons are vastly outnumbered by the truly great pitchers coming into their own. If we eliminate Van Poppel, Puleo, and Jack Kramer (a journeyman pitcher benefiting from the decreased talent level during World War II), we're left with a Hall of Famer (Hal Newhouser), two future ones (Johnson and Pedro Martinez), one of the better starters of the 1960s (Jim Maloney), and Duane Ward, who in the early 1990s might have been the best set-up man in baseball history.

Whatever Halladay started doing differently last year, let's hope he keeps doing it, because he's on to something big. The path he's following has been covered by some of the great pitchers in baseball history. But let's not get too excited yet. Remember, Todd Van Poppel once walked this way, too.

Rany Jazayerli is an author of Baseball Prospectus. Click here to see Rany's other articles.
You can contact Rany by clicking here